package cn.edu.sjtu.literature.web.filter;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class CharacterEncodingFilter implements Filter {

	protected String encoding = null;
    protected FilterConfig filterConfig = null;
    protected boolean forceEncoding = true;
	
	public void destroy() {
		this.encoding = null;
        this.filterConfig = null;
	}

	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {
		
		if (forceEncoding || (request.getCharacterEncoding() == null)) {
            String encoding = selectEncoding(request);
            if (encoding != null) {
            	request.setCharacterEncoding(encoding);
            	response.setContentType("text/html;charset=" + encoding);             	
            }
        }
        chain.doFilter(request, response);
	}

	public void init(FilterConfig filterConfig) throws ServletException {
		this.filterConfig = filterConfig;
        this.encoding = filterConfig.getInitParameter("encoding");
        String value = filterConfig.getInitParameter("forceEncoding");
        if (value == null)
            this.forceEncoding = true;
        else if (value.equalsIgnoreCase("true"))
            this.forceEncoding = true;
        else if (value.equalsIgnoreCase("yes"))
            this.forceEncoding = true;
        else
            this.forceEncoding = false;
	}
	
	protected String selectEncoding(ServletRequest request) {
        return (this.encoding);
    }

}
